Lapping machine



July 30, 1946. F. omo

LAPPING' MACHI NE Filed Nov. 4, 1944 INVENTOR! FRANK omo BY ATTORNEY Patented July 30, 1946 UNITED STATES PATENT OFFICE LAPPIN G MACHINE Frank Orio, Long Branch, N. J.

Application November 4, 1944, Serial No. 562,009

(Granted under the act of March 3, 1883, as

2 Claims.

amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to improvements in lapping machines.

Due to the enormous demand created by the war for crystals of the piezoelectric type for frequency control purposes, mas production grinding methods have been developed. One important grinding or lapping machine has evolved from the drill press and is capable of simultaneously lapping a large number of crystals on both sides. Every effort has been made to perfect the machines to save time and materials and to simplify the lapping operation.

Such a machine is provided with two spaced, horizontally disposed, lapping plates, one above the other. Loosely positioned between said plates is a crystal carrier which holds a plurality of crystals. A rotary motion is imparted to said crystal carrier by the spindle of the drill press which operates through a small crank and thereby moves the crystals between the lapping plates. In some of these machines the upper lapping tion to provide positioning means for the upper lapping plate which, while allowing the two plates to be insulated from each other, are nevertheless not subject to rapid wear or breakage.

It is another object to provide positioning means which will allow the upper lapping plate to be placed in the machine and removed therefrom in a less exacting manner than required by the prior art machines.

It is still another object to provide a positioning means which will eliminate the dropping of spacer rods with the resultant loss of time and sometimes of rods.

It is a further object to provide positioning mean which, in ordinary use, do not separate from the machine but which may be moved aside plate is maintained in register with the lower plate by four, separable, spacer rods. The inner ends of said rods extend into holes about the periphery of said upper plate and their outer ends into vertical slots in aligning brackets secured to the base of the machine. In order to place the upper plate, which ordinarily weighs some ten to twenty pounds, into its operating position, the four spacer rods are inserted into the holes about the plates periphery and the plate is lowered into position manually. This is rather awkward and exacting as the rods drop out if the plat is not held exactly horizontally, and all four rods must be simultaneously guided into the four slots aforementioned. The result is that spacer rods are frequently dropped and sometimes lost, spacer rods and crystals are frequently broken, additional time is spent in making several attempts to perform this step and in making adjustments, and sometimes the job requires the services of two persons.

As the progress of the lapping operation is checked by periodically testing the crystals for frequency, the two lapping plates must be insulated from each other. Hence, the crystal carrier and the spacer rods are made of some insulating material, such as Bakelite. This results in rapid wear and frequent replacement of the rods.

It is, therefore. an object of the present invenbefore and after the lapping operation.

Other and further objects will become clear from the specification and claims hereinafter set forth.

The objects aforesaid are achieved by eliminating the separable spacer rods entirely. Instead, aligning bracket members are provided which in clude nonseparable spacer fingers, of insulating material. This precludes the possibility of dropping, losing or breaking said fingers, and avoids the necessity of carrying the heavy lapping plate with several easily separable spacer rods loosely disposed about its periphery. The said spacer fingers are pivotable so that they can be moved out of the way, thereby simplifying and making less exacting the operation of placing or removing the upper lapping plate and definitely making it a one man operation. Said fingers are also provided with replaceable metal tips at the point of wear, thereby making replacements less frequent and then requiring replacement of the tips only. The fingers are also adjustable to allow for lapping crystals of different thicknesses,

The novel features, which are believed to be characteristic of the invention, are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the embodiment set forth in the following description taken in connection with the accompanying drawing, in which Figure 1 is a perspective view of the lower portion of a crystal lapping machine embodying the present invention, the spacer fingers being shown in their operating positions;

Figure 2 is an elevational view of Figure l, the

spacer finger to the left being shown in its nonoperating position;

Figure 3 is an enlarged vertical cross sectional view of the left hand aligning bracket member of Figure 1; and

Figure 4 is a perspective view of the aligning bracket member of Figure 3.

The lapping machine, shown in the drawing, stands upon a base I, having .a flat, horizontally disposed, top surface I3. Resting upon said surface I3 is a metal, disc-like, lower lapping plate l5, the top, fiat, horizontal surface I1 of which forms the lower lapping surface of the machine. Positioned about the lower lapping plate l are four aligning bracket members I9, each of which is secured to the base II by means of a machine screw 2|.

Spaced above the lower lapping plate I5 is a 23 are a plurality of crystals 3| to be lapped.

Said crystals3| are retained in spaced relationship relative to each other by a carrier 33 which is a disc of insulating material, such as Bakelite, of smaller diameter than the lapping plates I5, 23 and pierced by a circular axial hole 33 and a plurality of holes 35 shaped to loosely receive the crystals 3|. The carrier 33 is not as thick as the crystals 3| which are to be lapped. The machine may be provided with several carriers 33 of different thicknesses and having different sized holes 35 so that a suitable carrier may be used in lapping crystals of a particular thickness and size. I v

Axially positioned above the lapping plates I5, 23 is a spindle 31 which is rotatable by a motor (not shown). Secured to the lower end of the spindle 31 is a crank 33 fitted with a depending pin 4| which is of a size to make a rotatable fit in the center hole 33 of the carrier 33.

Each of the aligning bracket members IS includes a bracket 43 of metal which is in the shape of an elbow. The horizontal arm of said bracket 43 is pierced by an elongated vertical hole 45 receivable to one of the screws 2| aforementioned. The upper end of the vertical arm of the bracket 43 is bifurcated to form two upwardly extending projections 4-1 with a slot 49 therebetween. I

A spacer finger 5| of insulating material, such as Bakelite, has one narrow outer end which fits loosely into the slot 49 between the projections 41. Said spacer finger 5| is pivoted to said projections 41 by means of a pin 53 which extends through the two projections 41 and the narrow end of the spacer finger 5i, and is held in place by a cotter pin 55. The wider inner end of the spacer finger 5| is tipped with a metal cap plate 51, having a curved face. Said cap plate 51 is held in place by a machine screw 59 and is kept from rotating about said screw by a pin 6| secured to the cap plate 51 and extending into a horizontal hole in the end of the spacer finger 5|. Threaded transversely into the bottom of the spacer finger 5| is a vertically disposed adjusting screw 53, the head of which rests upon the lower end of the slot 49. A

Electrical contact is made with the two lapping plates I5, 23 by means of two disengageable plugs 55 attached to the end of the double conductor cable 61.

In operation of the lapping machine shown in the drawing, the lower lapping plate [5 is placed upon the base coaxial with the spindle 31. The four aligning bracket members I9 (their spacer fingers 5| all being flipped upwardly and outwardly to their nonoperating positions as shown at the left side in Figure 2) are then loosely screwed to the base H by means of the screws 2|. They are moved inwardly until they abut the periphery of said lower lapping plate |5 whereupon the screws 2| are tightened. The crystal carrier 33 is then placed upon the lower lapping plate l5 and the proper number of crystals 3| are dropped into the holes 35.

The upper lapping plate 23 is then lifted manually by the handles 29 and lowered onto the crystals 3!. Although it should be in register with the lower plate I5, it will be seen that, as the spacer fingers 5| are out of the way, there will be sufficient room to allow the said upper lapping plate 23 to be placed easily into its approximate position. This is much simpler than is the case in prior art machines, where exact positioning while the plate is being lowered is requisite. After the plate 23 is resting upon the crystals 3|, it becomes a simple matter to fiip the spacer fingers 5| upwardly and then inwardly to their substantially horizontal operating positions (as shown in Figures 1 and 4), the upper plate 23 being slid horizontally slightly, if necessary, to enable the said fingers 5| to be dropped into place. The adjusting screws E3 may be set for the thickness of the particular crystals being worked on.

The depending pin 4| of the crank 39 is then lowered into the center hole 36 of the carrier 33 through the central aperture 21. Rotation of the spindle 31 will then cause the crystals 3| to move about horizontally between the upperand lower lapping surfaces I1, 25 a, suitable grinding compound being applied. The progress of the lapping is ascertained by a frequency meter (not shown) through the conductor cable 51 and the plugs 65.

It will be noted that the inner ends of the horizontal arms of the brackets 43 hold the lower lap ping plate l5 in place and the spancer fingers 5| hold the upper lapping plate 23 in position in register with it. When the spacer fingers 5| are flipped to their outward, nonoperating positions, they should pivot through at least ninety degrees so that they say put and do not fall back by themselves. Actually, in the preferred embodiment shown in the drawing, said spacer fingers 5| pivot through well over one hundred eighty degrees so that said fingers and their adjusting screws 53 swing completely out of the way.

To remove the crystals 3 after they have been lapped, the depending pin 4| is raised by raising the spindle 31. The spacer fingers 5| are again flipped upwardly and outwardly and the upper lapping plate 23 is raised out of the way to expose the crystals 3|.

It is to be noted that, both in placing and in removing the heavy upper plate 23, meticulous accuracy of movement is not requisite and no loose parts can fall out. Hence, the operation is greatly simplified, thereby saving labor and time and precluding the breakage of crystals and a parts of the machine. Also wear is largely localized in the cap plates 51, which may be periodically replaced. Obviously, however, such replacement is much less frequent than the replacement of spacer rods made of Bakelite and the like, as in conventional machines.

Although the embodiment herein described to illustrate the present invention is shown in connection with a crystal lapping machine, it will be understood that it is within the spirit of the invention to apply it to other lapping or grinding machines and to other uses.

What is claimed is:

1. An aligning bracket member, comprising a bracket, having a horizontal arm and a vertical arm, an elongated hole extending vertically through said horizontal arm, two vertical projections at the upper end of the vertical arm, a spacer finger of insulating material, the outer end of said spacer finger being positioned between the projections aforesaid, a pivot pin extending through the said projections and the spacer finger, the spacer finger being pivotable about said pivot pin through more than ninety degrees, a replaceable tip on the inner end of the spacer finger, a screw threaded transversely into the spacer finger and adapted to rest upon the vertical arm to adjustably support the spacer finger in a substantially horizontal position.

2. An aligning bracket member comprising a bracket, said bracket including substantially vertically and horizontally disposed arms, means on said horizontally disposed arm to allow the bracket to be translated horizontally to a plurality of positions and rotated about Vertical axes, a spacer finger pivotably secured to the vertically disposed arm, means to adjustably support said finger in a substantially horizontal operating position, said finger being pivotable from its said operating position upwardly through in excess of ninety degrees to a nonoperating position.

FRANK ORIO. 

